A pursuit spacecraft from the planet Tatooine is attempting to catch up with a Trade Federation cruiser. As measured by an observer on Tatooine, the cruiser is traveling away from the planet with a speed of 0.6c. The pursuit ship is traveling at a speed of 0.8c relative to Tatooine, in the same direction as the cruiser. What is the speed of the pursuit ship relative to the cruiser?

I think you need this equation. In your case, $s$ is the velocity of the cruiser, you can make $v$ the velocity of the pursuit ship, and $u$ is the motion of the pursuit ship relative to the cruiser. Solve for $u$. Does that work for you?